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that can be adjusted from 4- 75 ft. to 10' 75 ft.

1009. Drawing of H.M.S. " Dwarf." (Scales 1 : 12 and 1 : 48.)
Woodcroft Bequest, 1903. N. 88.

This shows the vessel with the Woodcroft adjustable screw in place ;
it was, however, never so fitted, although some trials with it on H.M.S.
" Minx "gave very satisfactory results.

1010. Woodcroft's adjustable pitch propeller. Woodcroft
Bequest, 1903. N. 150.

This is a small example of a propeller similar to those in the models
(a) and (c), No. 1007, and as patented by Mr. Bennet "Woodcroft in 1832-44.
The blades are forged from boiler plate.

1011. Model of Maudslay's self-adjusting screw. (Scale 1 : 16.)
Maudslay Collection, 1900. N. 2237.

By this arrangement, patented by Mr. Joseph Maudslaj^ in 1848, the
blades of the screw, when the engines are not working, turn into the plane
of the shaft and thus reduce the sailing resistance.

There are two propeller blades, each having a shank passing completely
through the boss and capable of turning in the same. One blade is further
aft than the other, and the two shanks are formed with teeth by which they
gear together ; at the termination of the teeth are stout lugs or stops, by
which the swing of the blades is limited between the fore-and-aft position
and the working pitch. The centre of area of each blade is considerably
behind the axis of the shank, so that the action of the water causes the
desired turning ; a locking clutch, moved by a lever from the deck, secures
the blades in either position and permits of the engines being reversed.

1012. Stern model with adjustable pitch propeller. (Scale
1 : 16.) Contributed by Messrs. Maudslay, Sons and Field,
1858. N. 113.

In this are embodied the improvements patented by Joseph Maudslay,
in 1853 on a screw propeller patented by him in 1848.

On the stem of each blade and within the boss of the propeller, is fixed
a short arm connected by links to a lug cast on a collar sliding on a pro-
longation of the propeller shaft. The collar is moved endwise by bell-crank
levers worked by a screw from the deck ; this causes the blades to turn on
their axes till the most efficient angle for a particular speed is found, or till



337

in line with the stern post when the vessel is under sail alone. The whole
apparatus is mounted in a frame whereby it can be raised to the level of
the vessel's deck.

1013. Model of adjustable pitch Griffiths propeller. (Scale
1 : 8.) Contributed by Robert Griffiths, Esq., 1860.

N. 438,

This represents the general proportions of blade and boss patented by
Mr. Griffiths in 1849, and subsequently so largely adopted.

The leading features of the Griffiths' screw are that the central portion
is filled up by a spherical or ellipsoidal boss about one-third the diameter of
the screw, while the blades have their greatest width at their mid-length,
and taper to the point more on the leading than the trailing side.
Mr. Griffiths first tried his screw on a steamer at Bristol about 1850 ; it
was afterwards applied to the S.S. " Laristoii " by one of the Clyde builders,
and then the Admiralty allowed it to be tested on H.M.S. " Fairy," when
such results were obtained that its use rapidly extended. The screw showed
an increase of speed over older forms, but its popularity is chiefly due to
its other advantages, such as increased strength of boss, separable blades,
reduced vibration, and less resistance when used as an auxiliary. The large
boss was introduced to reduce the centrifugal motion of the water, and to
dispense with that part of the screw where the whirling action is greatest.

Both blades of the model are adjustable in pitch, from 18 to 24 ft. In
the first arrangement, patented in 1853, the cylindrical stem of a blade has
snugs on it which fit into a corresponding hole in the boss ; when inserted it
is rotated through, a right angle and retained in the desired position by
cotters and packing pieces. In the second arrangement, patented in 1858,
a cotter through the stem of a blade rests in a sector-shaped slot in the
boss, and adjustment is made by varying the packing pieces on its sides ;
both ends of the boss are smoothly finished off by caps that enclose the
cotters, etc.

1014. Adjustable pitch propeller. Presented by W. Hewitt,

Esq., 1863. N. 852.

This construction of screw was patented by Mr. Hewitt in 1855. On.
the axis of each of the four blades, which are circular discs, is a toothed
sector, gearing with a bevel wheel fixed to a sleeve on the propeller shaft.
This sleeve can be rotated by worm- gearing, and thus the pitch of the
blades can be simultaneously adjusted ; when this is accomplished the
sleeve can be locked to the shaft by a sliding collar which acts as a clutch.
The worm is then put out of gear by lowering its bearings.

1015. Models of auxiliary propellers. (Scale 1 : 8.) Lent by
the Rev. P. A. Fothergill, B.A., F.R.S., late R.N, 1871. .

N. 1325.

Two models are shown in which by an invention made by the lender in
1865, the propeller blades are so arranged as to automatically set into the
position of least resistance when not being used, while they return to
the correct pitch when the engine power is exerted. The blades have each
a cylindrical stem, fitting into the boss and provided with a stop by which
the pitch angle is prevented from being reduced below the working value.
The reefing is performed by the resistance of the water, but it is not
clear by what means the arrangement is modified so as to permit of driving
astern.

1016. Model of stern frame with adjustable pitch propeller.
(Scale 1 : 8.) Lent by W. J. Griffiths, Esq., 1873.

N. 1363.

This is an adjustable screw patented by Mr. R. Griffiths in 1868. The
screw is intended as an auxiliary, and can be adjusted from within the ship,
u 6773 Y



338

Inside the boss the shank of each blade is provided with an arm, which
is connected by a link to a collar, secured on a sleeve that is loose on the
propeller shaft. The after end of the sleeve has turned in it a groove, in
which fits a brake which can be tightened on the collar by a screwed tube
from a hand-wheel on deck. While this is being done the engines are made
to rotate the shaft slowly, thus screwing the collar along and feathering
the blades. In the tube to the brake is a rod resting on an eccentric
groove cut in the collar ; the rise and fall of this rod indicates the amount
of adjusting that is being performed.

1017. Models of adjustable pitch, screw propellers. (Scale
1 : 8.) Lent by W. Andrews, Esq., 1899. N. 2180.

These show two modifications of a method of altering the pitch of screw
propeller blades, patented by Mr. H. B. Young in 1866-70. The shanks
of the two blades are inserted in a hollow boss, and extend nearly through
it, but are retained in position by arms projecting from them. These
arms are controlled by a nut on a screwed rod which extends through the
main boss, and can be turned by a suitable key. This key is manipulated
entirely from within the vessel, after the propeller has been placed in the
vertical position. In one of the models there is an additional key, which
actuates a wedge for locking the blades after they have been set.

1018. Reversible propeller (working). Lent by the Gaines
Reversible Propeller Co., Ltd., 1910. N. 2587.

With the application of internal combustion engines to marine pro-
pulsion, some independent reversing arrangement became necessary. The
difficulty of obtaining motion in the reverse direction can be obviated simply
by changing the pitch of the propeller blades : the arrangement shown,
patented in 1904 by Mr. Gr. Spicer, is of this kind.

The blades turn on cylindrical shanks with spherical bearings within the
boss, the after half of which is removable. The propeller shaft is hollow to
accommodate the rod for moving the blades ; this ends inside the boss in a
piece of triangular section, in each face of which is a pin fixed eccentrically.
The pins engage in slots in the enlarged ends of the blades, and form virtual
cranks about which the blades can rotate when the rod is moved axially.
. To effect this there is a lever working in a fixed quadrant, which operates by
means of pins projecting from it, a collar sliding on the propeller shaft.
This collar is pinned to the rod inside, a slot in the propeller shaft allowing
of axial movement. The collar, rod, and shaft rotate as one.

In some forms of this gear a hand- wheel and screw mechanism is used to
operate the lever. By this means very slight changes in the pitch of the
blades can be made to suit any conditions of running. The lubricant used
inside the boss is thick grease. The stern bush and thrust block are shown.



LIFTING AND SIMILAR SCREW PROPELLERS.

1019. Stern models with lifting screws. (Scale 1 : 36.) Con-
tributed by J. Seaward, Esq. N. 423-4.

These show methods proposed in 1846-9 by Messrs. Seaward and Capel
for applying an auxiliary screw to a 90-gun ship, at the time when it was
decided to fit a large number of wooden sailing ships with steam power.

(a) In this arrangement the propeller is abaft the rudder, and is carried
in a frame which can be raised by a screw in a nut secured to it. The shaft
terminates in a flat -sided crosshead which fits into a notch cut in the face
of the propeller boss. The rudder is expanded so that, although pene-
trated by the propeller boss, it is not cut in two nor is its motion interfered
with.

(b) This plan resembles the above, but to avoid the alterations to the
rudder the propeller is placed on one side of the stern post, the rudder
being simply notched to give the necessary clearance.



339

1020. Stern model with, lifting screw. (Scale 1 : 24.) Con-
tributed by Messrs. Maudslay, Sons and Field, 1861.

N. 420.

This is fitted with an arrangement for lifting an auxiliary screw, intro-
duced by Joseph Maudslay in 1846.

The screw is two-bladed, and is carried in a frame formed of two links
and a cross-head which slides in guides, and can be lifted by rope tackle
to the deck level ; the connection to the shaft is made by a slot and feather
in the face coupling.

1021. Model of stern with screw propeller. (Scale 1 : 96.)
Maudslay Collection, 1900. N. 2235-6.

This arrangement was proposed about 1850 for fitting existing line-of-
battle ships with auxiliary screws without extensive structural alteration.
The propeller is placed abaft the stern post and a rudder post is added
outside it, the head being accommodated by a rounded projection at the
stern. The screw is connected to the shaft by a slotted face-coupling, and
is arranged for lifting in the way patented by Mr. Joseph Maudslay in
1846. (See No. 1020.)

In another model relating to the arrangement, to a scale of 1 : 64, the
lifting propeller is disengaged by moving the tail shaft forward until its
squared end is clear of the boss.

1022. Model of stern frame with, lifting screw. (Scale 1 : 12.)
Presented by Messrs. Bullivant & Co., 1902. N. 1895.

This represents the two-bladed screw propeller and lifting arrangements
of H.M.S. " Blenheim," a wooden 72-gun ship fitted with an auxiliary screw
in 1847 by Messrs. Seaward and Capel.

The end of the screw- shaft was flanged out and a slot cut partially across
it to receive the end of the screw, which was supported in bearings formed
in a frame which could be lifted in its guides by rope tackle from a winch.
The propeller was 16 ft. diam., 20 ft. pitch, and 3 3 ft. long ; on trial in 1849
it drove the vessel at 5 '8 knots with 938 indicated h.p.

1023. Model of stern frame with lifting screw. (Scale 1 : 12.y
Presented by Messrs. Bullivant & Co., 1902. ' N. 1891.

This shows the hydraulic arrangement of John Seaward for lifting a
screw when not steaming, fitted in 1848 to H.M.S. "La Hogue," an
existing line-of -battle ship, which thereby became one of the first screw-
propelled men- of war.

The screw is hung in a frame which slides in guides and is raised by
telescopic hydraulic rams arranged in the guides. The end of the propeller
shaft is flanged out and slotted to receive a corresponding projection on the
tail shaft.

1024. Stern model with auxiliary propeller. (Scale 1 : 36.)
Contributed by Messrs. Jackson and Watkins, 1861.

N. 431.

This shows a vessel's stern fitted with a screw shaft placed on one side
of the rudder. The propeller is two-bladed, and each blade is cottered
through its stem into a central casting that serves as a boss.

1025. Stern model with Seaward's folding propeller. (Scale
1 : 16.) Presented by Messrs. Bullivant & Co., 1902.

N. 1892.

This arrangement for reducing the resistance of an auxiliary propeller
when the engines are not being used was designed by Mr. Seaward in 1848.
The propeller is two-bladed, but is cut into short lengths which can be

y 2



340

tamed so as to cover one another, in a similar way to that in which a lady's,
fan closes ; in this way the width can be so reduced that but little projects
beyond the deadwood. The foremost section is fixed to an outer annular
shaft, and the hindmost section to the internal or main shaft ; the intermediate
sections have pins and notches so that by rotating the hollow shaft upon
the main one, by means of worm gear, the fan can be opened or closed.

1026. Stern model with unshipping propeller. (Scale 1 : 24.)
Contributed by W. H. Crispin, Esq., 1861. N. 434.

This is fitted with a screw carried in a narrow frame, which is removable
sideways by means of ropes from two deck winches.

1027. Lifting propeller (working). Presented by the Rev.
J. M. Kilner, 1878. N. 1505.

This arrangement, patented by Mr. Kilner in 1870, has been tried in a
boat and on a ship of 1,274 tons. When propelled by one man the boat
attained a speed of 3 47 knots, but the mechanism is also adapted for being
driven by steam power.

The propeller is a two-bladed screw, carried in a frame which is
lowered through a well at the stem so that the screw is below the keel level
when in use. The propeller is rotated by bevel gear from a vertical shaft
driven by a modified double-ended winch handle; but a long horizontal
connecting-rod has been used in a similar arrangement when employing
several men.

1028. Model of stern with auxiliary screw propeller. (Scale
1 : 48.) Lent by J. Wimshurst, Esq., F.R.S., 1902.

N. 2298.

The arrangements here represented, for reducing the resistance created
by the propeller when a vessel is proceeding under sail, were patented by
Mr. H. Wimshurst in 1840-59.

The propeller is four-bladed, but is formed of two two-bladed screws
provided with clutch faces where their bosses are in contact, and only one
screw is secured to the shaft, the other being free to move backwards
through 90 deg. When the propeller is in use the resistance of the water
keeps the blades apart, while at other times the loose portion can be so
turned that its blades are in contact with the fixed ones, and thus leave
but very little projecting beyond the deadwood.

To further reduce the resistance occasioned by the propeller when not
in use, two shutters are provided, hinged to the rudder and capable of being
swung back so as to enclose the folded propeller and cover the hole in the
deadwood ; two narrow flaps hinged to the stern post are added to retain
the shutters in position. When the propeller is in use the shutters are
swung round to the sides of the rudder, and there secured by a hinged
strap. The propeller is, moreover, so mounted that it can be unshipped
sideways, and then be brought upon deck in the manner shown in the model
of the S.S. " Novelty " (see No. 975).

1029. Stern model with auxiliary propeller. (Scale 1 : 36.)
Presented by the Institution of Civil Engineers, 1868.

N. 1191

The invention consists in an arrangement of shutters by which the
resistance of a screw that is not being driven is reduced. The screw is
two-bladed, and when in the vertical position it can be closed in by two
vertical shutters sliding in grooves. These shutters close in the projections
and secure regular stream lines when the ship is under sail.

Such an arrangement was patented by Mr. J. M. Hyde in 1857, and by
many others subsequently.



341

1030. Whole model of vessel with protected screws. (Scale
1 : 24.) Lent by W. J. Griffiths, Esq., 1874. N. 1362.

In 1873 Mr. R. Griffiths experimented with a clockwork driven model
arranged very much as in this example. The result obtained he considered
most promising, but soon afterwards he neglected the scheme in favour of
others of a less revolutionary character.

The model represents an armoured frigate, built with a circular tunnel
at each end sloping downwards in an easy curve to the bottom, and in each
tunnel is fitted a screw propeller with wide tipped blades. The screws were
in this way protected, while possibly a better supply of water was obtained
than when arranged in the ordinary manner.

Mr. Griffiths considered that by dividing the power between these two
screws an increase of 30 per cent, in the speed resulted over that obtained
with all of the power applied to a single screw at the stern ; a gain of 50 per
cent, in speed over the stem screw when an engine of equal power was
applied at the bow ; and that these tunnel screws gave 12*8 per cent, more
speed than ordinary twin screws with the same power and revolutions. He
found his best result when the water supplied was 60 per cent, greater than
the estimated requirement of the screw.

1031. Stern models with special arrangements of Griffiths
propellers. (Scale 1 : 24.) Lent by W. J. Griffiths, Esq.,
1882. N. 1571.

This group contains two half and three whole models of sterns,
showing certain arrangements of propeller introduced by Messrs. R. and
W. J. Griffiths.

(a) and (e) Represent twin and single screws respectively, arranged
under protecting concentric hoods fixed to the stern ; these are considered
to have increased the vessel's speed by 7 per cent.

(&) Illustrates a protector for screws, described in Mr. R. Griffiths' last
patent (1877). It is formed of two fixed cylinders concentric with the
screw, the inner one just clearing it and the outer one 1 ' 125 times its diam.
The arrangement has been fitted to several trawlers, and is stated not to
have reduced the speed.

(c) Shows a screw arranged 66 of its diam. further aft than the end
of the vessel's run, as patented by Mr. W. J. Griffiths in 1878. In this
position the screw is clear of the dead water, and it is claimed that it
gives an increase of 12 per cent, in speed over that obtained when further
forward.

(d) Shows an arrangement patented by Mr. R. Griffiths in 1853, in
which the propeller is placed abaft the stern post, the requisite space being
obtained by cutting away the rudder where necessary.

1032. Stern model with Mallory's propeller. (Scale 1 : 4.)
Lent by the Mallory Propeller Co., 1879. N. 1519.

This combined propelling and steering screw was introduced in 1878 by
Col. W. H. Mallory, of the United States.

The propeller is carried by a frame resembling a rudder, and is rotated
by bevel gearing from an engine on deck. As the screw is adjustable in
direction it will turn the vessel even when she has no way on. A modi-
fication of the arrangement has been introduced in which the screw is
directly driven by an enclosed electric motor receiving its current through
a flexible cable ; all such propellers are, however, limited to small powers.



MARINE PROPULSION OTHER THAN BY PADDLES

OR SCREW.

The earliest known method of propelling a raft or boat
through the water is by means of muscular effort applied to



342

paddles or oars, the former being the more primitive apparatus ;
nor does it appear that any means more effective than the long
oar to enable a man to employ his own effort has been discovered
down to the present day.

The adjustable sail acted on by the force of the wind, an
invention later than the oar since it requires some steering
power before it can be successfully employed, had been brought
to considerable perfection in prehistoric times as evidenced by
the earliest Egyptian monuments. The sail still remains the
only important appliance for utilising the energy of the wind,
although windmills driving propellers and kites for hauling
canal boats have been repeatedly tried, without any considerable
success.

Hydraulic propulsion, i.e., by admitting water near the bow
through a trunk and forcing it out near the stern, requiring
as it does simple power arrangements, has received much
attention. Between 1784 and 1793 James Rumsey in the
United States and later in England demonstrated by experiment
the feasibility of the method. John and Morris W. Ruthven
between 1839 and I860, employing a centrifugal pump, persisted
in this direction till, at the latter date, H.M.S. " Waterwitch "
was built to make comparative tests ; she attained a speed of
9 ' 25 knots, but the power developed would have given a higher
speed if exerted on a suitable screw propeller. The method,
however, has received a limited application in situations where
the propelling mechanism must be protected (see No. 50-4).

When the rotative steam engine had been sufficiently
developed to permit of attempts being made to apply it to
marine propulsion, almost every conceivable propeller was
tried. John Fitch in 1786-92 experimented with a series of
connected paddles, either at the sides or the stern, and actually
ran a boat so fitted for a short time in 1790. The idea has
been repeatedly revived since, and as late as 1845 on the
Thames a boat named the "Propeller" was driven by two
reciprocating dashboards. The action of a man sculling at
the stern with a single oar has also been imitated mechanically.
Earl Stanhope adopted Genevois's idea, i.e., a collapsible pro-
peller resembling the foot of an aquatic bird ; this he actuated
through a trunk by an engine on the centre line of a boat, but
the speed attained on actual trial in 1790-3 was disappointing ;
the idea was revived as late as 1882. Another method experi-
mented with was a chain of float boards passing over two
sprocket wheels at each side ; this was employed by Desblanc
in 1802 (see No. 1033).

The numerous methods of propelling canal boats by poles,
wheels or screws working against the bottom, have shown no
important advantages. A chain or rope resting on the bed of
the river, &c., and picked up by a power-driven wheel on the
boat, which thus hauls itself along, has had a wide application
for ferries, and to a limited extent on canals, where the power



343

lias been supplied through, an overhead conductor to an electric
motor on board. The latter system has been applied to drive
a screw propeller, but a more promising method is traction by
electric motors with overhead rails.

1033. Model of paddle-chain (working). (Scale 1:8.) Con-
tributed by the Commissioners of the 1851 Exhibition,
1857. N. 31.

This apparatus was patented by Mr. John Spurgin in 1837, as a means for
providing a shallow vessel with the equivalent of a paddle-wheel of large
diameter. A similar arrangement had been patented in France in 1802, by
Desblanc.

On each side of the hull is an endless pitch chain running round a
return pulley fore and aft, and over a large sprocket wheel between them,
fixed on the crank- shaft. To the chains are secured floats, which thus
describe a catenary curve of a dip that is adjustable by means of the sliding
bearings in which the return pulleys are carried.

Mr. Spurgin also patented this mechanism as a continuous elevator (see
Mechanical Engineering Collection).

1034. Model of reciprocating propeller (working). (Scale
1 : 48.) Maudslay Collection, 1900. N. 2232.

This arrangement of mechanically moved paddle has been frequently
proposed, probably on account of its being more compact than any form of
paddle-wheel. In the scheme represented there is a single steam cylinder
driving a crank- shaft on which are two flywheels, from each of which
extends a connecting-rod giving a horizontal reciprocating motion to a
concave board or float. A vertical movement is also introduced, by links
from the crosshead, and the compound motion thus given to the floats
causes them to describe oval curves, so that they are above the water during
the return stroke. The floats extend through a hole in the deadwood, and
overlap, but, owing to their alternate action, clear one another.

1035. Half-block model of H.M.S. " Waterwitch." (Scale
1 : 48.) Received 1869. N. 1317.

This was an armour-plated gunboat designed by the Admiralty, and
launched at Millwall in 1866.

She was propelled by a hydraulic reaction arrangement, introduced by



Online LibraryScience Museum (Great Britain)Catalogue of the naval and marine engineering collection in the ... museum .. → online text (page 48 of 58)